The invention relates to a Coriolis mass flowmeter with a measuring tube that can be excited into oscillation, an oscillation driver and/or an oscillation sensor, wherein the oscillation. driver and/or the oscillation sensor has a permanent magnet.
Mass flowmeters that work according to the Coriolis principle generally have at least one oscillation driver that excites the measuring tube into oscillation as well as two oscillation sensors, which register the achieved oscillation of the measuring tube. The determination of the mass flow is then definable, e.g. using the phase shift of the achieved oscillations between the two oscillation sensors.
The oscillation driver and oscillation sensors are generally assembled in such a manner that they have a permanent magnet as well as a magnetic coil in order to vibrate the measuring tube or, respectively register the oscillations of the measuring tube in an electrical manner. In order to attach the permanent magnet to the oscillation driver or, respectively, the oscillation sensors, it is generally provided with a hole so that it can be affixed with a screw lead through the hole. However, the magnetic field is negatively influenced by this sort of mounting screw. In addition, the permanent magnet is exposed practically without any defense mechanism to mechanical external influences such as bumping during transport or during installation, so that damage of the Coriolis mass flowmeter cannot be ruled out.